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J. Ermert, T. Blum, K. Hamacher, Heinz H. Coenen

Alternative syntheses of [^73,75Se]selenoethers exemplified for homocysteine[^73,75Se]selenolactone

The present work describes two radiosynthetic pathways to prepare homocysteine[⁷⁵Se]selenolactone 1 starting from n.c.a. [⁷⁵Se]selenite 2. It was achieved either by alkylation reaction of n.c.a. methyl[⁷⁵Se]selenide 4 or by hydrolysis of alkylated 1,3-dicyclohexyl[⁷⁵Se]selenourea 11.
N.c.a. methyl[⁷⁵Se]selenide 4 is available using sulfur as non-isotopic carrier. However, the radiochemical yield of the substitution of 2-tert.-butoxycarbonylamino-4-bromobutyric acid ethylester 5 with n.c.a. methyl-[⁷⁵Se]selenide is only in the range of 15-20%. Birch reduction of protected n.c.a. [⁷⁵Se]selenomethionine 6 formed leads to a RCY of 5-10% homocysteine[⁷⁵Se]selenolactone 1.
Alternatively, the synthesis of homocysteine[⁷⁵Se]selenolactone 1 is possible by hydrolysis of the corresponding [⁷⁵Se]selenouronium salt 11 available by addition of 2-tert.-butoxycarbonylamino-4-bromobutyric acid ethylester 5 to 1,3-dicyclohexyl[⁷⁵Se]selenourea 10. A method was developed for the synthesis of 1,3-dicyclohexyl[⁷⁵Se]selenourea 10 by addition of c.a. [⁷⁵Se]SeH₂ to 1,3-dicyclohexylcarbodiimide, which leads to 20-30% RCY of c.a. homocysteine[⁷⁵Se]selenolactone 1.

Radiochimica Acta, Oldenbourg Wissenschaftsverlag

Print ISSN: 0033-8230
Volume: 89, 11/2001
Pages: 863

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